Between 1968 and 1983, a San Francisco cartoonist becomes an amateur detective obsessed with tracking down the Zodiac Killer, an unidentified individual who terrorizes Northern California. His spree leaves citizens locked into a constant state of panic and baffled authorities scrambling for clues.
As two detectives remain steadfast in their devotion to bringing the elusive killer to justice, they soon find that the madman has control not only over their careers, but their very lives as well.